Razor-wire fence built by Slovenia is killing wildlife.
Photograph: Arthur Neslen for the Guardian

The death toll of animals killed by a razor wire fence designed to stop migrants crossing into Europe is mounting, amid warnings that bears, lynx and wolves could become locally extinct if the barrier is completed and consolidated.

The rising tally of dead roe and red deer is still mercifully small, but contested by local people who claim that it is being systematically under-counted.

Slovenia began erecting the barrier across 180km of its river border with Croatia last winter, as a temporary measure to staunch the flow of asylum seekers, mostly from Syria, Iraq and Afghanistan. Inadvertently, it has also created a huge obstacle to animals freely moving across the border in a wildlife rich corner of Europe.

But even though the human migration crisis has dramatically eased, Slovenia’s interior ministry is seeking a change in the law to prevent environmental factors from slowing the barrier’s extension.

A government spokesperson said that while refugee numbers were falling, “there are still more than 57,000 migrants in Greece. The situation in Turkey remains very uncertain after the military coup. There is a political crisis in Macedonia, and an increasing number of migrants are gathering in Serbia, which lacks sufficient accommodation capacities. Also, the number of people travelling the migrant route across the Mediterranean to Italy has increased again.”

While the fence is supposed to be a temporary measure, fears that the crisis could be prolonged were heightened when the government signalled its intent to fence its entire 670km border with Croatia in December.

Researchers from the University of Ljubljana report of several tonnes of razor wire being stockpiled in the open at military barracks near the Croatian border, ready to be unfurled at short notice.

Its deployment could be fast-tracked by an amendment to the state border control law that is currently being debated. The proposal, which the Guardian has seen, would exempt fence-related construction from “regulations governing environmental protection, nature conservation, and water”.

Geographical isolation would throw the continued survival of the region’s 10 wolf packs into doubt, disrupting centuries-old mating migration routes, according to a peer-reviewed paper published in the journal PLOS Biology.

Other carnivores could fare even worse. “For the Dinaric lynx, the construction of the razor wire fence may just be the last push for the population to spiral down the extinction vortex,” the study’s authors said.

The mountain cat was only reintroduced to the Dinaric mountain chain in 1973, after human activity wiped it out.

Most of the animals killed by the razor wire so far have been roe and red deer, but it is yet to reach key forest areas. Stretches of the barrier are already covered by vegetation or seasonally submerged by the 292 km-long Kolpa river, which straddles the two countries’ border.

Many of the deer are thought to have strayed into the fence while foraging. Once snagged, they propel themselves further into the concertina wire in a bid to escape, only tangling themselves further before eventually dying from blood loss, or exhaustion.

A dead deer snagged on the fence in Radenci in Slovenia. Photograph: Courtesy of Martin Lindic

Zrinka Domazetović, head of biodiversity in Croatia’s environment ministry, said that: “when an animal is tangled in wire, you see it right away. Other impacts, which can have an even more detrimental impact on wildlife, cannot be so easily seen.”

Conservation scientists say that the greatest threat to wildlife comes from two-metre-high panel fences which are increasingly being used along the barrier’s route to mollify public opposition to the razor wire.

New and as yet unpublished research by Slaven Reljic, one of the PLOS Biology paper’s authors, suggests that hemming in the region’s 1,500 bears for longer than a decade would assure their irreversible decline.

“In Croatia the annual bear-hunting quota is set at 10-15% [of the entire population] and in Slovenia it can reach almost 20%,” he said. “If the two populations are closed in, neither will be sustainable.”

The picture is further darkened by a “trophy-hunting” trend towards killing the largest bears – older males which command the highest prices. That results in a disruptive competition between juvenile bears which struggle to take their place, Reljic says.

But hunters’ associations in both countries may play an important role in conserving the bear populations they depend upon, according to regional academics. As well as monitoring the animals, many hunters detain poachers, build gates in the border fence and even lure animals back from the razor wire with food dispersals.

This is vital work because, as Domazetović puts it, “bears and wolves don’t understand political borders”. One collared bear, named after Slaven Reljic, crossed the national boundary three times last year in a six month period.

Zdenka Štucin, a judge from Ljubljana who opposes the fence. Photograph: Arthur Neslen for the Guardian

Hostility to the fence is widespread in the Upper Kolpa valley where the rampart snakes through. Zdenka Štucin, a judge from Ljubljana with a second home in Petrina, described it as “something horrible”.

“It makes me feel anxious,” she said. “Once, my daughter slipped as we were on our way to swim in the river. She almost fell and instinctively reached out for something. She grabbed the razor wire and it cut into her hand.” She bled profusely.

But the razor fence is a patchy and - for humans - easily passable mishmash. It is peppered with gaping holes and absent tracts, where the fence is not yet built, or already removed by public opposition.

“The barrier was just a psychological trick to signal to our Croatian partners that something was being done,” said Dr Boštjan Pokorny, an assistant professor at Slovenia’s national forestry institute.

A Croatian government spokesman said the barrier was a “panic reaction” by Slovenia that had caused “great damage” to political relations and local livelihoods.

“For the wild animals with habitats in the border area, this razor wire is an impassable obstacle which causes many of them to be mortally hurt every day,” the official told the Guardian. “If the fence lasts for 10 years or more, the long-term negative effects will be seen in the worsening genetic codes of the animals.”

A migrant carries a child as they continue their journey in Dobova, Slovenia October 2015. Photograph: Srdjan Zivulovic/Reuters

“The refugee crisis was a personal affair for me as I was a refugee myself during the war in Croatia,” said Aleksandra Majic, who manages the University of Ljubljana’s bear and wolf conservation projects. As a high-school student, she was evacuated during the Balkan wars, first to Zagreb and then to Canada.

“I have to actively forget about my beliefs of how people should be treated because I want to be seen as objective when we talk about this fence’s effect on wildlife,” she added. “It is a huge challenge.”

One of the fence’s few vocal supporters in the Upper Kolpa valley cited the police capture of a group of Syrian migrants in nearby Osilnica the day before. Peter Madronic, a young campsite worker, said the refugees were too “culturally different” from Croats to be integrated.

“Most people think that the fence is useless or senseless but I have a lot of contact with the police and they told me that migrants trying to cross the border here can be returned if we have a fence,” he said. “Without it, they cannot.”

Another Croatian campsite owner, Martin Lindić, whose land in Radenci borders the fence, said that the structure was absurd, as humans could bypass it by crossing a local bridge.

“When the military forces came here and began fixing the fence, it felt like some kind of military occupation was starting,” he said. “People got organised and we cut the concertina wire during a demonstration against the fence.”

A deer that had been caught in the fence. Photograph: Courtesy of Martin Lindic

The authorities removed sections of the razor wire in the protest’s aftermath. More fencing was removed after a Croatian complaint to Brussels that it breached the birds and habitats directive.

A spokesperson for the European commission said that the Slovenian government’s activities were being “monitored closely”. A European court case could follow.

Since the days of the former Yugoslavia, the beautiful hilly landscape has been a popular tourist site for rafting, canoeing, kayaking and fishing. Dragan Arih, a ranger in Croatia’s Risnjak national park, said that extending the barrier to his forest would be “terrible, awful, catastrophic”.

“The animal migrations would be stopped and when the Kolpa floods – as it did last year – the wire would be claimed by the river and then you have another problem for the fish – and for the tourists.”

The president of the Fara tourist authority, Dr Stanko Nikolic, an 85-year-old physician from Belgrade who moved to Slovenia half a century ago, said that there had been a 50% decline in regional tourism revenues since the wall was built.

The valley was once a borderless frontier for rural Croats and Slovenes who felt more in common with each other than with their capital cities.

“There are still a lot of contacts between people on both sides of the river,” Nikolic said. “They want to remove this ‘temporary’ fence. If it becomes permanent, I’m afraid that our common life will collapse into two fragments.”

The fence had already caused the deaths of “several dozens” of local animals, he added. Such estimates though, are contested. A new survey by the Slovenian hunting association, the Slovenian government’s accredited monitor, will say that only around 15 animals, have died on the wire so far, mostly red deer.

Croatian and Slovenian people protest against the border fence in December 2015. The pamphlet reads Wire Killer. Photograph: Ales Beno/Getty Images

“We were very surprised the number was so low,” said Pokorny, who also heads up the Slovenian hunting association’s game management commission. “After the hunting association met with the foreign ministry and police officers last December, many openings were made in the fence along the animals’ pathways and we believe they are finding a way to use them.”

Some local people say that the figures do not count animals that die from their wounds in the river or in forests. Igor Barbara, secretary of the Croatian hunting lodge, said that seven red deer had been killed in the 10km stretch of fence bordering his hunting ground alone. He had found others with razor lacerations, floating dead in the river.

Lindić cited another 10 deer killed on his small section of the barrier. He also claimed to have seen several retreats by animals which had become enmeshed in razor snarls. A bear had also been entangled before escaping, he said.

“I think that about 100 animals have died from entanglement on the fence,” Lindić told the Guardian.